merge::records_in_range and optimizer

sql/sql_select.cc:
  optimizer bug fixed. (what's the difference between s->records ans s->found_records ?)

mysql-test/r/merge.result

@@ -35,10 +35,10 @@ insert into t1 select NULL,message from t2;
 create table t3 (a int not null, b char(20), key(a)) type=MERGE UNION=(test.t1,test.t2);
 explain select * from t3 where a < 10;
 table	type	possible_keys	key	key_len	ref	rows	Extra
-t3	range	a	a	4	NULL	10	Using where
+t3	range	a	a	4	NULL	18	Using where
 explain select * from t3 where a > 10 and a < 20;
 table	type	possible_keys	key	key_len	ref	rows	Extra
-t3	range	a	a	4	NULL	10	Using where
+t3	range	a	a	4	NULL	16	Using where
 select * from t3 where a = 10;
 a	b
 10	Testing
@@ -561,3 +561,38 @@ a
 1
 2
 drop table if exists t1, t2, t3, t4, t5, t6;
+DROP TABLE IF EXISTS t1, t2;
+CREATE TABLE t1 (
+fileset_id tinyint(3) unsigned NOT NULL default '0',
+file_code varchar(32) NOT NULL default '',
+fileset_root_id tinyint(3) unsigned NOT NULL default '0',
+PRIMARY KEY  (fileset_id,file_code),
+KEY files (fileset_id,fileset_root_id)
+) TYPE=MyISAM;
+INSERT INTO t1 VALUES (2, '0000000111', 1), (2, '0000000112', 1), (2, '0000000113', 1),
+(2, '0000000114', 1), (2, '0000000115', 1), (2, '0000000116', 1), (2, '0000000117', 1),
+(2, '0000000118', 1), (2, '0000000119', 1), (2, '0000000120', 1);
+CREATE TABLE t2 (
+fileset_id tinyint(3) unsigned NOT NULL default '0',
+file_code varchar(32) NOT NULL default '',
+fileset_root_id tinyint(3) unsigned NOT NULL default '0',
+PRIMARY KEY  (fileset_id,file_code),
+KEY files (fileset_id,fileset_root_id)
+) TYPE=MRG_MyISAM UNION=(t1);
+EXPLAIN SELECT * FROM t2 IGNORE INDEX (files) WHERE fileset_id = 2
+AND file_code BETWEEN '0000000115' AND '0000000120' LIMIT 1;
+table	type	possible_keys	key	key_len	ref	rows	Extra
+t2	range	PRIMARY	PRIMARY	33	NULL	5	Using where
+EXPLAIN SELECT * FROM t2 WHERE fileset_id = 2
+AND file_code BETWEEN '0000000115' AND '0000000120' LIMIT 1;
+table	type	possible_keys	key	key_len	ref	rows	Extra
+t2	range	PRIMARY,files	PRIMARY	33	NULL	5	Using where
+EXPLAIN SELECT * FROM t1 WHERE fileset_id = 2
+AND file_code BETWEEN '0000000115' AND '0000000120' LIMIT 1;
+table	type	possible_keys	key	key_len	ref	rows	Extra
+t1	range	PRIMARY,files	PRIMARY	33	NULL	5	Using where
+EXPLAIN SELECT * FROM t2 WHERE fileset_id = 2
+AND file_code = '0000000115' LIMIT 1;
+table	type	possible_keys	key	key_len	ref	rows	Extra
+t2	const	PRIMARY,files	PRIMARY	33	const,const	1	
+DROP TABLE IF EXISTS t1, t2;

mysql-test/t/merge.test

@@ -204,3 +204,36 @@ create temporary table t6 (a int not null) TYPE=MERGE UNION=(t4,t5);
 select * from t6;
 drop table if exists t1, t2, t3, t4, t5, t6;
 
+#
+# testing merge::records_in_range and optimizer
+#
+
+DROP TABLE IF EXISTS t1, t2;
+CREATE TABLE t1 (
+  fileset_id tinyint(3) unsigned NOT NULL default '0',
+  file_code varchar(32) NOT NULL default '',
+  fileset_root_id tinyint(3) unsigned NOT NULL default '0',
+  PRIMARY KEY  (fileset_id,file_code),
+  KEY files (fileset_id,fileset_root_id)
+) TYPE=MyISAM;
+INSERT INTO t1 VALUES (2, '0000000111', 1), (2, '0000000112', 1), (2, '0000000113', 1),
+(2, '0000000114', 1), (2, '0000000115', 1), (2, '0000000116', 1), (2, '0000000117', 1),
+(2, '0000000118', 1), (2, '0000000119', 1), (2, '0000000120', 1);
+CREATE TABLE t2 (
+  fileset_id tinyint(3) unsigned NOT NULL default '0',
+  file_code varchar(32) NOT NULL default '',
+  fileset_root_id tinyint(3) unsigned NOT NULL default '0',
+  PRIMARY KEY  (fileset_id,file_code),
+  KEY files (fileset_id,fileset_root_id)
+) TYPE=MRG_MyISAM UNION=(t1);
+
+EXPLAIN SELECT * FROM t2 IGNORE INDEX (files) WHERE fileset_id = 2
+AND file_code BETWEEN '0000000115' AND '0000000120' LIMIT 1;
+EXPLAIN SELECT * FROM t2 WHERE fileset_id = 2
+AND file_code BETWEEN '0000000115' AND '0000000120' LIMIT 1;
+EXPLAIN SELECT * FROM t1 WHERE fileset_id = 2
+AND file_code BETWEEN '0000000115' AND '0000000120' LIMIT 1;
+EXPLAIN SELECT * FROM t2 WHERE fileset_id = 2
+AND file_code = '0000000115' LIMIT 1;
+DROP TABLE IF EXISTS t1, t2;
+

sql/sql_select.cc

@@ -1219,7 +1219,7 @@ make_join_statistics(JOIN *join,TABLE_LIST *tables,COND *conds,
       select->quick=0;
       if (records != HA_POS_ERROR)
       {
-	s->found_records=records;
+	s->records=s->found_records=records;
 	s->read_time= (ha_rows) (s->quick ? s->quick->read_time : 0.0);
       }
     }
@@ -1944,7 +1944,7 @@ find_best(JOIN *join,table_map rest_tables,uint idx,double record_count,
 		    records
 		    This gives the formula:
 		    records= (x * (b-a) + a*c-b)/(c-1)
-		    
+
 		    b = records matched by whole key
 		    a = records matched by first key part (10% of all records?)
 		    c = number of key parts in key